Decolorization of sugar melts



Patented Aug. 7, 1945 DECOLORIZATION OF SUGAR MELTS George P. Vincent, Poughkeepsie, N. Y., assignor to The Mathieson Alkali Works, Inc., New York, N. Y., a corporation of Virginia No Drawing. Application February 26 1941,

Serial N0. 380,642

'1 Claims.' (01.12146) My invention relates to improvements in refining sugar melts, including syrups, more particularly to decolorizati'on of such sugar melts,. and has as its primary objects improvements in the efllcacy and economy of such refining operations.

For many years the decolorizati'on of sugar melts depended upon defecation followed by treatment with bonechar. Then, over a period of years, the use of activated decolorizing carbon supplanted the use of bonecha'r to an important extent. Several years ago it/was proposed to bleach the sugar melt chemically prior to treatment with activated decolorizing carbon. Economic margins in sugar refining are narrow, small differentials in cost thus become important and consequently these advances have found a place in practical operations to the extentthat they I developed economic advantage.

portion 01' a chlorite for a relatively large propor tion 0! the calcium hypochlorite in such an operation with a substantially reduced consumption of total bleaching agents, hypochlorite plus chlo-. rite, measured either in terms oi total weight of reagents or in terms of total available chlorine, with consequent important savings in reagent costs. I do not fully understand the mechanism of the reactions involved, but apparently the hypochlorite activates the chlorite.

In accordance with'my invention, the sugar melt to be decolorized is treated with calcium hypochlorite in the presence of a chlorite and with a phosphate deiecating agent and thereafter is treated with adsorbent, particularly an activated decolorizing carbon. The hypochloritechlorite treatment is with advantage carried out at a temperature approximately 70-110 F. The precise order in-which the several treating agents are added to the melt in the chemical treatment is not essential. but certainadvantages are secured by a g the calci m yp chlorite after the phosphate defecating agent, particularly it 1 sodium chlorite is the chlorite used, as will'appear. The products of defecation are with ad v ventional practice;

vantage separated from the-melt prior to the treatment with the adsorbent. 'The chemical bleaching treatment of my invention may with advantage be applied directly to; light colored sugar melts. With darker melts it is usually advantageous to subject the melt to treatment with lime and a phosphate defecating agent and to separate the products of this defecation prior to the chlorite-hypochlorite treatment.

In referring to chlorites, Irefer particularly to sodium chlorite, NaClOz', and calcium chlorite,

Ca(C1O2) 2. In referring to phosphate defecatlng agents, I refer to the known defecating agents of this class such'as sodium phosphates, acid calcium phosphates and phosphoric acid. In reterring to adsorbents, I refer to adsorbents such as activated decolorizingcarbon, bonechar and calcined bauxite. I

My invention is applicable to a wide variety-of sugar refining operations. It will, however, be further described in more detail in connection with particular embodiments which illustrate the application of my invention to sugar meltsproduced from raw sugar.

Starting with raw cane sugar the sugar is washed, for example, in 'centrifugals as in con- The washing operation produces a washed raw sugar and aflinations, the latter being handled in the conventional way. The washed raw sugar is then melted with-water to form the melt to be treated and decolorized. This melting operation may be carried out at moderate temperature or it may be carried out at.

elevated temperature and the melt subsequently cooled to the temperature appropriate for further processing. The washed raw sugar may be melted in water or in 'sweet water, water containing some sugar valuesfrom some other step in the refining operation. The pH value of the sugar melt is with advantage then adjusted, for example by the addition of lime water, so that at no time during the further processing will the pH value of the melt drop below about 6.8 or some higher minimum limit.' The pH value of the melt may tion tom'elts or syrups of any particular concentration. v

Ii tlie melt is relatively light in color, calcium acid phosphate, sodium chlorite, and calcium hypochlorite are added in that order and the 're-' sulting reactions are allowed to proceed, for example for one hour at a temperature of about 85-95 F. The sodium chlorite may be the com-- mercial product containing for example 130% available chlorine and the calcium hypochlorite may be for example the commercial product containing for example 70% available chlorine. The proportions of the several reagents, in percentages by weight on the sugar solids present, may approximate for example for sodium chlorite 0.0088%, for calcium acid phosphate 0.027% and for calcium hypochlorite 0.065%.

It sodium chlorite is used and if the calcium hypochlorite is added after the acid calcium phosphate as indicated, bubbles of gas liberated by the reactions will attach themselves to the particles of solid precipitate forming through the melt with the result that the products of defecation will, with reasonable care, be carried .to the surface of the melt in the treating receptacle as a floating scum from which the clear treated liquor can readily be separated by decantation. If the calcium hypochlorite is added before the acid calcium phosphate, or ii precipitation is initiated as by the use of calcium chlorite prior to introduction of the calcium hypochlorite, this result is not uniformly attained and some other or some supplemen'tal means for separating the products of defecation must be used. The products of defecation, for exam le, can be separated by filtration and in such a filtration it is advantageous to use a filter aid such as diatomaceous earth.

The sugar melt is then treated with an ad-' sorbent, with particular advantage with activated decolorizing carbon, as in conventional practice. For example, the sugar melt following separation of the products of defecation may be treated period of 10 or 15 minutes at a temperature of 80-90 F. The carbon treatment may also be carwith 0.1% of activated decolorizing carbon for a V ried out for longer periods and at higher temperatures; periods of treatment as long as one hour or more and temperatures as high as 2002 10 F. I are useful. Following this treatment the suspended carbon is separated as in conventional practice, for example by filtration. The filtrate constitutes the refined and decolorized product produced by my invention. I

If the melt, following adjustment otthe pH value, is relatively dark'in color, it is usually advantageous to subject it to a preliminary defecation before subjecting it to the chlorite-hypochl01-te treatment. For example, this preliminary defecation may be carried out by addition of lime and calcium acid phosphate or phosphoric acid as defecation is conveniently practiced in conjunction with the use of bonechar or activated carbon. Also, if the melt is relatively dark in color, the proportions of the several treating reagents may be increased. For example, the pro-- effect the same decolorizations with about onehalf of the consumption of chemical reagents and with from about one-third to less than one-fifth of the consumption of the adsorbent, activated decolorizing carbon for example, required to attain the result by conventional practices. The economic advantage of such savings with respect to carbon or other adsorbent required will be selfapparent. Even though the cost per unit of available chlorine as chlorite is greater than that as hypochlorite, I have in this manner been able to reduce the cost of chemical reagents, as distinguished from carbon or other adsorbent, to one-hall or less.

The refined and decolorized-melt can be used as a syrup, as is or followingi'urther concentration or dilution. Or, this defined decolorized melt may be subjected to concentration and crystallization, for example in multiple efiect evaporators followed by a vacuum pan crystallizer and granulating-and cooling drums as in conventional practice, to produce the sugars of commerce. My invention is applicable to syrups or other melts whether or not they are produced from raw sugar. My invention is also applicable to sugar melts generally irrespective of their particular concentration, provided only that they are melts, that treating the' melt with an activated decolorizing carbon.

2. In refining sugar melts, the improvement which comprises treating the melt at a temperature approximating 70-ll0' F. with calcium hypochlorite in the presence of a chlorite and witha phosphate defecating agent and thereafter treating the melt with an activated decolorizing carbon.

portions may approximate for example for sodium chlorite 0.026%, for calcium acid phosphate 0.073% and for calcium hypochlorite 0.196%. Similarly, the proportion of activated decolorizing c'arbon used may be increased, for example, to

Activated decolorizing carbon is a particularly advantageous adsorbent. in the process of my invention, in that it has but a limited effect upon the pH value of the processed melt. Calclned bauxite may be used in the same way, although somewhat larger quantities may be required. Instead of treating the melt with carbon or bauxite, following the chlorite-hypochlorite treatment, it

may be percolated through, or otherwise treated 3. In refining sugar vmelts, the improvement which comprises successively adding to the melt sodium chlorite, a phosphate dei'ecating agent and calcium hypochlorite, separating the prodnets of defecation and thereafter treating the melt with an activated decolorizing carbon.

' 4. In refining sugar melts, the improvement which comprises treating the melt with calcium hypochlorite in .the presence of a chlorite and with a phosphate defecating agent, separating the products of defecation and thereafter treating the melt with an activated decolorizing carbon.

5. In refining sugar melts, the improvement which comprises treating the melt with lime and a phosphate defecating agent, separating the products of defecation, then treating the melt with calcium l'lypochloritein the presence of a 2,aa1,oeo

chlorlt and with a phosphate defecating agent an? thereafter treating the melt withan adsorben "6. In refining sugar .melts, the improvement which comprises treating the melt with' calcium hypochlorite in the presence of a chlorite and with a phosphate deteeating agent and thereafter treating the melt with an adsorbent.

' GEORGE P. VINCENT. 

